Explosive compositions containing an aromatic nitro compound and calcium phosphate



U.S. Cl. 149-2 5 Claims ABSTRACT OF THE DISCLOSURE In an explosivecomposition comprising fusible aromatic nitro compounds, the improvementwhich comprises calcium phosphate fume in a minor proportion effectiveto improve detonation characteristics, thermal stability or exudationcharacteristics. The calcium phosphate fume is characterized by lowdensity and high specific surface area.

The invention relates to the improvement of the properties of explosivesand explosive compositions of fusible aromatic compounds, particularlyTNT and trinit-robenzene, or mixture-s of these nitro compounds withnitramines and/ or with nitric acid esters, e.g. mixtures with tetry-land/or nitropentaerythrol (nitropenta), including e-ute tics with tetrylor nitropenta, by adding finely divided calcium phosphate to them. Knownadditives, such as metal powders or desensitizers can be included.

The calcium phosphate has been manufactured by mixing phosphoric acidwith the required amount of calcium nitrate or calcium chloride to forma clear solution or paste, and by spraying this mixture into a currentof hot inert gas at temperatures of 190 to 450 C. The production of thecalcium phosphate fume is described in DAS 1,196,166, issued toChemische Fab-rik Kalk. We call this product calcium phosphate fume. Thecalcium phosphate fume is a finely divided product having a largespecific surface area, in general about l50 m. /g., and having anextremely low bulk density in general about 0.010.07 g./cm. It is addedto the explosive components in minor proportion, e.g. a quantity of 0:1to 15 preferably 0.2 to5% by weight of the composition.

It has been found that the addition of the abovementioned calciumphosphates to the fusible aromatic nitro compositions and compounds, forexample, TNT and trinitrobenzene, surprisingly modifies particularly thefollowing three properties;

(1) The capability of detonation is improved;

(2) Thermal stability and shock resistance; and

'(3) The exudation of impurities is largely prevented.

Also particularly surprising was the extent to which the properties ofthe castable explosives according to the invention changed. This is madeapparent hereinafter by a comparision betwen TNT charges with andwithout the addition of calcium phosphate.

EXAMPLE 1 Sticks of TNT were cast with and without the addition ofcalcium phosphate. The length of the sticks was 20 cm., and the diameterwas varied. The sticks of explosives were ignited with a pressed pelletof 15 g. of tetryl and were stood up on a lead plate which served as anindicator for complete detonation. The tests were performed without anyenclosure. A stick of TNT having a diameter of 50 mm. and no additivewould not propagate the detonation and the lead plate was undamaged.

3,496,039 Patented Feb. 17, 1970 If the TNT contained 1% calciumphosphate (specific surface area 15 m. /g.; bulk density of 0.03 g./cm.the charge detonated perfectly all the way through the stick, even at adiameter of 10 mm.

Cast TNT cylinders 200 mm. long and 28 mm. in diameter and having aspecific weight of 1.60 g./cm. could not be detonated with No. 8aluminum blasting caps. With the addition of 1.5% calcium phosphate,such explosive sticks detonated perfectly all the way through. Thedensity of this explosive composition according to the inventionamounted to 1.58 g./cm. The tests were performed with any wrapper orenclosure. At the end of the stick opposite the blasting cap, adetonation speed of 6600 m./s. was measured. If 12 or 15% calciumphosphate was added to the molten TNT, a paste-like composition wasobtained having a specific weight of 1.61 g./cm. and 1.64 g./cm.respectively. Cylinders 200 mm. long and 28 mm. in diameter preparedfrom this composition could not be detonated, even with a No. 6 blastingcap containing 0.5 g. of PETN and 0.5 g. of potassium chloride as abooster. The detonation speed amounted to 6500 and 6200 m./s.respectively.

The advantage of the improved detonatability consists mainly in the factthat TNT charges can be detonated easily without the use of boostersmade of pressed tetyrl, PETN, hexogen or TNT. In fact, cast TNT chargescontaining the calcium phosphate additive according to the invention canbe used as boosters for explosives that are diflicult to initiate. Forexample, slurries can be detonated in blasting holes with detonatorsmade of TNT and the calcium phosphate additive according to theinvention, instead of charges of cast pentolite such as are used today.

The improvement in thermal stability and shock resistance is clarifiedby the following experiments: 0.4 g. of TNT with and without theaddition of calcium phosphate according to the invention was finelyground and placed in a glass test tube. This tube was placed in a'heated bath of Woods metal which was adjusted to a constanttemperature. The time it took for the TNT to flash or explode wasdetermined. The longer this time is, the better the explosion toleratesthermal stress. The time for TNT amounted to 38 seconds, and for TNTcontaining the addition of 2% calcium phosphate according to theinvention amounted to seconds. The falling weight impact tests wereperformed according to Koenen Ide (Explosivstotfe, N0. 2, February 1961,pp. 3436). With a weight of 5 kg. and a 10 cm. drop, the firstexplosions produced in the TNT were without additive. If the TNTcontained the addition of 2% calcium phosphate according to theinvention, the beginning of the reactions was not obtained until thedrop amounted to 20 cm. The following results were measured for thetotal of 6 tests of each explosive at heights of 10, 20, 30, 40, 50 and60 cm.:

98: TNT,

2 calcium TNT phosphate No reaction 24 28 Partial reaction 0 4 Explosion12 4 paper and exposed for 20 hours to a temperature of 70 C. Thisproduced spots of greater or lesser size on the filter paper. The largerthe diameter of these spots, the greater is the tendency of theexplosive to exudation. For a TNT with a solidification point of 80.47C., a spot diameter of 44 mm. was measured. If increasing amounts ofcalcium phosphate are added to this TNT, the following spot diametersare measured:

Calcium phosphate content (percent): spot diameter, mm. 44

The advantage of the addition of calcium phosphate according to theinvention consists, according to this eX- periment, in the fact thatcast TNT charges can be stored at higher temperatures, e.g., in hotsunlight, without the occurrence of exudation.

EXAMPLE 2 The experimental results described in Example 1, involvingexplosive charges of TNT with and without the addition of calciumphosphate according to the invention were obtained in like manner alsowith explosive compositions made of aromatic nitro compounds and metalpowders. A cast stick (200 mm. long, 28 mm. diam.) made of a mixture of75% TNT and 25% aluminum powder with the addition of 2% calciumphosphate (specific surface area 15 m. /g.; bulk density 0.03 g./cm.according to the invention could be detonated with a No. 8 aluminumblasting cap, for example, while the same mixture without the additionof the calcium phosphate could not be initiated with a No. 8 aluminumblasting cap. A mixture of 47.6% TNT and 52.4% aluminum required 59seconds to flash or explode at a temperature of 340 C. However, if 1part of calcium phosphate was added to the mixture, the time required toignite it amounted to 67 seconds. The size of the spot produced bybleeding was measured at 38 mm. for the mixture of 75% TNT(solidification point 80.47 C.) and 25% aluminum. With the addition of1% calcium phosphate according to the invention, the diameter of thespot amounted to only 11 mm.

EXAMPLE 3 In the case of explosive compositions containing a suflicientamount of nitramines or nitric acid esters, the improvement ofdetonatability by the addition of calcium phosphate according to theinvention is of no importance. Consequently, it has not been our aim tobring about an improvement of the initiability of such compositions. Inthe case of such explosive mixtures, flashing or explosion was producedat 238 C. after the following periods- Mixture A:

40% TNT (solidification point 80.47 C.),

60% hexogen seconds 33 Spot diameter mm 40 Mixture B:

39% TNT (solidification point 80.47 C.),

60% hexogen, 1% calcium phosphate (specific surface area 12 m. /g.; bulkdensity 0.07 g./cm. "seconds" 40 Spot diameter mm 10.5

EXAMPLE 4 In the case of explosive compositions of TNT (solidificationpoint 80.47 C.), hexogen and powdered aluminum, flashing or explosionwas produced at 235 C. within the periods specified below, the specificweights and spot diameters being also given- 4 Mixture A:

TNT percent 35 Hexogen do 40 Aluminum powder do 25 Time seconds Spec.weight g./cm. 1.85 Spot diameter mm Mixture B:

TNT percent 30 Hexogen do Aluminum powder d0 25 Desensitizer consistingof 4.2 parts paraflin wax, 0.7 part nitrocellulose, 0.1 part lecithin do5 Time seconds 29 Specific weight g./cm. 1.77 Spot diameter mm MixtureC:

TNT percent 34.5 Hexogen do 40.0 Powdered aluminum do 25.0 Calciumphosphate (spec. surface area 42 m. /g.; bulk density 0.01 g./cm. do 0.5Time seconds 46 Specific weight g./cm. 1.84 Spot diameter mm 8.3

From this it is apparent that the addition of calcium phosphateaccording to the invention not only produces an excellent desensitizingeffect and an obvious reduction of bleeding as compared with theconventional desensitizers, but also that the castings made from suchcompositions also have a greater specific weight than those made withthe conventional desensitizers.

EXAMPLE 5 In the case of explosive compositions made from TNT(solidification point 80.47 C.) and tetryl (this two component mixtureis known as tetrytol), the following spot diameters were measured andflashing or explosion occurred at 230 C. after the following periods-Mixture A:

TNT percent 30 Tetryl d0 70 Time seconds 28 Spot diameter mm 48 MixtureB:

TNT percent 30 Tetryl do 69 Calcium phosphate (spec. surface area 18 m./g.;

bulk density 0.025 g./cm. do 1 Time seconds 42 Spot diameter mm 18 Inthese two experiments the explosive was not in powder form, but wasplaced in the test tube in the form of a piece weighing 0.4 g.

EXAMPLE 6 In the case of explosive compositions of TNT (solidificationpoint 80.47 C.) and PETN (pentaerythritol tetranitrate), flashing orexplosion occurred at 230 C. after the periods of time specifiedhereinafter, and the spot diameters were as described- Mixture A:

TNT percent 50 PETN do 50 Time seconds 27 Spot diameter (at C.) mm 41Mixture B:

TNT percent 50 PETN do 49 Calcium phosphate (spec. surface area 20 m./g.;

bulk density 0.02 cm. do 1 Time seconds 34 Spot diameter (at 65 C.) mm13 In these two experiments the explosive was placed in the test tubenot in powder form but in the form of a piece weighing 0.4 g.

EXAMPLE 7 The following are the spot diameters and the time periodsrequired to produce the flashing or explosion of explosive mixtures oftetryl, trinitrobenzene and hexogen at 230 C.

Mixture A:

Tetryl percent 16 Trinitrobenzene do 24 Hexogen do 60 Time seconds 30Spot diameter mm 50 Mixture B:

Tetryl percent 16 Trinitrobenzene do 24 Hexogen do 59 Calcium phosphate(spec. surface area m. /g.;

bulk density 0.03 g./cm. do 1 Time seconds 38 Spot diameter mm 19 Thespot test was performed at 75 C. over a period of 2 hours.

EXAMPLE 8 The addition of calcium phosphate to explosive com positionsaccording to the invention can also be combined with the addition ofother desensitizers. The desensitizing effect of such combined additivesin this case can be increased considerably if, for example, a mixture ofchlorinated naphthaline with a softening point of 116 C. is used as adesensitizer together with the calcium phosphate (spec. surf. area 15 m./g.; bulk density 0.03 g./cm. For explosive compositions made fromtetryl and TNT (solidification point 80.47 C.), and known as tetrytol,the following are the spot diameters and the time periods required toproduce flashing or explosion at 230 C.

Mixture A:

Tetryl percent 70 TNT do 30 Time seconds 28 Spot diameter (at 60 C.) mm48 Mixture B:

Tetryl percent 69 TNT do 30 Chlorinated naphthaline do 1 Time seconds 43Spot diameter (at 60 C.) mm 50 6 Mixture C:

Tetryl percent 69 TNT do 30 Calcium phosphate do 1 Time seconds 42 Spotdiameter (at C.) mm 18 Mixture D:

Tetryl percent 68 TNT do 30 Calcium phosphate do 1 Chlorinatednaphthaline do 1 Time seconds 53 Spot diameter (at 60 C.) mm 20 In these4 experiments the explosive was not placed in the test tube in powderform, but in the form of a piece weighing 0.4 g.

The specific surface area was measured according to Blaines test. Thistest is described in the directives by the Verein Deutscher Ingenieure(VDI) (Association of German Engineers) No. 2031 of October 1962 underthe title Feinheitsbestimmungen an technischen Staeuben and can beobtained from the VDI-Verlag GmbH, Dusseldorf, Germany.

What is claimed is:

1. In an explosive composition comprising fusible aromatic nitrocompounds of the group trinitrotoluene and trinitrobenzene, theimprovement which comprises calcium phosphate fume having a specificsurface area of about 1050 m. g. and a bulk density of about 0.01-0.07g./cm. in a minor proportion effective to improve detonationcharacteristics, thermal stability or exudation characteristics.

2. Explosive composition according to claim 1, wherein the calciumphosphate fume is present in amount of about 0.145% by weight of thecomposition.

3. Explosive composition according to claim 2, said amount being about0.25% by weight of the composition.

4. An explosive composition according to claim 1 containing a materialof the group nitramines, nitric acid esters, and mixtures thereof.

5. An explosive composition according to claim 1 and containing metalpowder.

References Cited UNITED STATES PATENTS 3,271,212 9/1966 Riedl et a1149106 X CARL D. QUARFORTH, Primary Examiner S. I. LECHERT, JR.,Assistant Examiner US. Cl. X.R.

mg? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,496,039 Dated Feb. 17, 1970 Ioventofls) Adolf Berthmn, l.

It is certified that error appear in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

F T I C 201. Zfline l2 change "with" to ---without-.

.- P smusumo SEALED L I (SEAL) "Atteat: L

Edward'n'nmha' *2" wmma E. sudw .m. Attesting Officer Q 5. Oomissiqnqiforjetents

